The goal of this work is to characterize the gluctuation in kinetic parameters of rat striatal tyrosine hydroxylase due to changes in pH and ionic concentration of the reaction mixture. As a part of this project, it is also our objective to determine the optimal conditions to observe the effect of cocaine on tryosine hydroxylase and adenylate cyclase activity. We have also attempted to correlate changes in tyrosine hydroxylase activity with changes in adenylate cyclase activity in animals treated with cocaine.